We will study the deposition and clearance of inhaled radioactive tagged particles in normal subjects and patients. The studies will be done on the total lung and on regions within the lung. In the deposition studies, the patterns of deposition of inhaled particles in the lung are to be studied by using various patterns of respiration and different particle sizes. The studies of mucociliary clearance will be performed using both humans and beagle dogs. The effects of various drugs on the clearance rate and patterns will be studied. The mucociliary clearance pattern will be correlated with the deposition pattern of the inhaled particles. We also are carrying out extensive model calculations on the deposition of inhaled particles in the airway generations. We have developed a computer program which can give us particle deposition information for a given set of conditions such as particle diameter or breathing pattern. We are using our deposition model in conjunction with our clearance model in an effort to further understanding of particle deposition and clearance on the basis of airway generations.